Material layers can be formed on a substrate, such as to provide one or more functional or non-functional layers of an electronic device. In one approach, film layers on such devices can be fabricated in part via vacuum deposition of a series of thin films onto the substrate using any of a number of techniques, including without limitation, chemical vapor deposition, plasma enhanced chemical vapor deposition, sputtering, electronic beam evaporation, and thermal evaporation. However vacuum processing in this manner is relatively: (1) complex, generally involving a large vacuum chamber and pumping subsystem to maintain such vacuum; (2) wasteful of the raw material being deposited, because a large fraction of the material in such a system is generally deposited onto the walls and fixtures of the interior of the deposition chamber, such that more material is generally wasted than deposited onto the substrate; and (3) difficult to maintain, such as involving frequently stopping the operation of the vacuum deposition tool to open and clean the walls and fixtures of built-up waste material. In the case of substrates larger in surface area than generally available silicon wafers, these issues present further challenges.
In certain applications, it can be desirable to deposit a film in a specified pattern. In another approach, a blanket coating can be deposited over the substrate and photolithography can be considered for achieving desired patterning. But, in various applications, such photolithography processes can damage existing deposited film layers. A so-called shadowmask can be used to pattern a deposited layer directly when using a vacuum deposition technique. The shadowmask in such cases comprises a physical stencil with cut-outs for the deposition regions that can be, for example, manufactured out of a metal sheet. The shadowmask is generally aligned to, and placed in proximity to or in contact with, the substrate prior to deposition, kept in place during deposition, and then removed after deposition.
Such direct-patterning via shadowmask adds substantial complexity to vacuum-based deposition techniques, generally involving additional mechanisms and fixturing to handle and position the mask precisely relative to the substrate, further increasing the material waste (due to the waste from material deposited onto the shadowmask), and further increasing a need for maintenance to continuously clean and replace the shadowmasks. Such thin masks can be mechanically unstable over large areas, limiting the maximum size of substrate that can be processed, and it is therefore the case that again, for substrates larger in surface area than generally available silicon wafers, these issues are especially challenging.